iMessage out of whack... how to "reset"

I had iMessage working just fine with the latest iOS8 on my iPad, iPhone & Yosemite OSX on my MBP... then after a system restart on my MBP a week+ ago iMessage is all out of whack. It works fine and as expected on my iOS devices (iPad & iPhone), but on my MBP, while I can receive & send messages, I have the following symptoms:

• No one resolves to their name... only phone numbers are listed for the other person in the conversation. This includes people I've sent messages to or received.


• When I sent a message, I can find the person by name & autocomplete, but when I accept the person from autocomplete, it resolves to their number.


• All recipients show up as red... for instance if you hover over the name/number, usually it shows a blue selection box, but for me they are all red.

I've tried signing out & back in, but that didn't work. I don't have any contacts in iCloud as I am on a hosted Exchange (Office 365) where all my contacts are. This is how it was setup since I got my MBP 1yr ago so I know this works and it still works on my iOS devices.

Everything I've seen talks about syncing your contacts to iCloud... but I've never needed to do that in the past and even when I manually copy one contact over, that has their name, email & correct phone number, it still won't resolve them to their name, only their number.

Any ideas how to reset this as everything I'm doing isn't working :(